The invention relates to a method of and an apparatus for horizontal and vertical guidance of cutter drive shields in open as well as closed spaces by advancing individual cutters of a cutter drive shield according to the predetermined sequence.
There is known a method for the horizontal and vertical guidance of cutter drive shields in closed, as well as open, spaces, whose construction and operation is to be described below for the purpose of illustrating the possibilities for guidance.
The known cutter drive shield consists essentially of a support frame, a drive or advance frame and of cutter planks comprising leading and trailing sections, the latter of which serve temporarily as a lining of the tunnel wall and are supported on the support frame.
In order to drive the shield forward, individual cutters are locked to the drive frame. Hydraulically actuated drive rams which are effective as between the support frame and the drive frame advance portions of the cutter shield which requires only relatively small forces. The static friction between the remainder of the cutter shield and the earth resting thereon constitutes an abutment of the hydraulically advancing cutter shield elements which thus do not exert reactive forces against the permanent tunnel lining during their advance.
All cutter planks being advanced, the drive frame, to which all cutters have been locked, advances the support frame by the length of the stroke of the hydraulic ram, and a new working cycle may begin.
The region of the trailing cutter section constitutes the outer casing for introducing the lining concrete, whereby the advancement of the drive shield may be pursued continuously independently of the setting time of the introduced lining concrete. Once a region of concrete is exposed in the rear follower, the interior form is pulled forward and the next region is concreted.
The guidance of the cutter drive shield is possible due to the reaction forces which occur when individual planks at a predetermined side of the shield are advanced. For example, if the cutter drive shield is to be driven in a horizontal plane, for example in a right turn, several cutters are simultaneously advanced in the direction of motion on the right side. The reaction forces which thus occur tilt the support frame, thereby introducing the curved drive motion. Subsequently, the direction is stabilized by the advance of individual cutters on the left side.
In corresponding manner, it is possible to perform a vertical guidance. If the known cutter drive shield is to be guided downwardly, a few side cutters which are located at the bottom of the cutter shield periphery at the left and right sides are simultaneously advanced or else the bottom cutters are advanced. The remaining lateral cutters are subsequently advanced in pairs, i.e., individually on each side. If the cutter drive shield is to be guided upwardly, a few lateral cutters which are located on the left and right sides at the top of the circumference of the cutter drive shield are simultaneously advanced. In this manner, the support frame is raised somewhat. This upwardly directed position is stabilized by individual advance of the bottom cutters.
Accordingly, the known method of maneuvering [Wilhelm Stuber: Westfalia- REPORTS, Dec. 1976, item 5.2] in curves is based on a tilting of the support frame which occurs when the sum of the forward driving forces of those cutters which are simultaneously advanced on one side is greater than the friction which exists between the support frame and the cutter.
It is a decisive disadvantage of the known method for controlling the shield advancement direction that the force conditions which lead to a tilting of the frame are not defined and depend on a multitude of factors, such as the specific ground friction, the top loading, the loosening, etc. Due to the undefined force conditions and especially because of the compulsive forces indirectly exerted on the cutter drive shield due to the tilting of the frame in the direction of intended curve, an exact guidance is possible only within limits and the guidance operation must be continuously controlled during the advance of the cutter drive shield and may have to be corrected. Furthermore, for example during the driving of a right-hand curve, as seen in the direction of advance, the tilting of the frame causes a reduction of the support for the cutters on the left side. For this reason, these cutters move inwardly during their advance which generates additional hollow spaces or loosening. Furthermore, generally only curves having very large radii may be evacuated in this fashion.